User Guide

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[head] Table Settings
These entries are specific for TrueType rendering. We do not recommend
you modify them if you are not sure of what you are doing.
LowestRecPPem
This parameter controls the lowest PPM at which the TrueType
rasterizer is allowed to apply instructions
FontDirectionHint
This [head] table parameter defines font direction, which may
have the following values:
0: Fully mixed directional glyphs
1: Only strongly left to right
2: Like 1 but also contains neutrals
-1: Only strongly right to left
-2: Like -1 but also contains neutrals.
A neutral character has no inherent directionality. Spaces and
punctuation are examples of neutral characters